LTE: Why does "UE Time Zone IE" send from MME to PGW via SGW ?

Question

Hi Friends,
I saw somewhere that MME will also do a DNS query for P-GW. As i know S-Gw will do a query for P-Gw address. Is there any situation that MME will do a query for P-GW address using APN? and after this query how MME will use the P-Gw Address.

and is there any possibility of Doing DNS query by P-Gw to get any other nodes Ips and under what conditions P-Gw will do a DNS query?

Answer 1

operator will do performance analysis by received UE Time Zone/ULI in CDR's (on Rf/Ro interface). Hence MME will send UE time zone value to SGW and PGW. if SGW/PGW will generate CDR(Charging Data Record) then SGW/PGW should include UE Time Zone value in this CDR and send it to offline/online charging server.so, whenever time zone changes, then MME will inform this change to SGW/PGW on next S11&S5S8 message.

Answer 2

Question is not clear, but if I got it then it's very simple.

Because there is no other way. Check how the network is built.